The Local site is the first site you open. This could be on your PC, or it could be located on the dark side of the Moon - but it's still the Local site. In Remote Site View the local site is always the left column.
The Remote site is the site you publish to. Again the physical location is immaterial - it could be on your PC or in the next city. In Remote Site View the remote site is always on the right.
Local to Remote: files on the Local site are sent to the Remote site, that is from Left to Right in Remote Site View
Remote to Local: files on the Remote site are moved to the Local site - from Right to Left in Remote Site View.
Synchronize: files are moved in both directions. The Changed files on both sides are moved to the other side, and Unmatched files are copied to the other site. This can be messy unless you know what is going on.
For details of the status codes see the publish states page.
First, if you don't have a local copy, publish the online site back to your PC. Close the online site, and open the copy on your PC.
I always prefer to work on a site on my PC - mistakes can be rectified before they become public.
If the site on your PC is the result of publishing from the live site, then any unwanted files will also be on the live site.
One way to test this is to open the sites in Remote site, or Publishing, view . Login to the Remote Site.
There is a drop down near the top left of the window which normally says "View - Folder Contents". Change this to "Files in Conflict"
In both panes a list of files will be shown with status of either Conflict or Unmatched. Ignore the files in Conflict, but decide whether the unmatched files are wanted or not - these will be in one pane or the other, depending on whether Local to Remote or Remote to Local is selected near the bottom right corner.
Look at the unmatched files in both panes - toggle between panes by using the "Local to Remote" and "Remote to Local" radio buttons at bottom right. Delete the files you don't want, and publish the others (highlight the files and click the Blue arrow in the middle of the screen) so they are on both sites.
Important: Deleted files cannot be recovered. There may be some files that are in one or other of the webs that you wish to keep, but not in the website. Publish these as above, but make a note to deal with them later.
Now, look for files that are not used.
This report will show all those files that cannot be reached from the Home Page.
Click on the "Links To" column (this column is not available in FrontPage 2000). This sorts the files in the list according to the number of links going to it - just because you can't get to the file directly from the Home Page, does not mean the file is not being used. Note that in the example report to the left left (click to enlarge) the highlighted file is unlinked - but has 14 links to it. Other files have various numbers of links to them from files.
Other cleanup operations involve changing the pages themselves. Changing <font> tags to CSS, Shared Borders to DWTs, removing excess code and similar tasks. This can be done on a page by page basis, as and when a page is amended.